This invention is directed generally to turbine blades, and more particularly to hollow turbine blades having an intricate maze of cooling channels for passing fluids, such as air, to cool the blades.
Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures. As a result, turbine blades must be made of materials capable of withstanding such high temperatures. In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures.
Typically, turbine blades are formed from a root portion at one end and an elongated portion forming a blade that extends outwardly from a platform coupled to the root portion at an opposite end of the turbine blade. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. The cooling channels in the blades receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots. Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade.
Operation of a turbine engine results is high stresses being generated in numerous areas of a turbine blade. Some turbine blades have outer walls, referred to herein as housings, formed from double walls, such as an inner wall and an outer wall. Typically, cooling air flows through a cavity defined by the inner and outer walls to cool the outer wall. However, uneven heating in the inner and outer walls of a turbine blade still often exists.
Thus, a need exists for a turbine blade that effectively dissipates heat in a turbine blade.
This invention relates to a turbine blade capable of being used in turbine engines and having a cooling system including, at least, a cavity positioned between two or more walls forming a housing of the turbine blade. The turbine blade may be formed from a generally elongated blade and a root coupled to the blade. The blade may have an outside surface configured to be operable in a turbine engine and may include a leading edge, a trailing edge, a tip at a first end, and one or more cavities forming a cooling system. The root may be coupled to the blade at an end generally opposite the first end for supporting the blade and for coupling the blade to a disc.
The cooling system may include a cavity defined by an inner wall and an outer wall forming the housing of the blade and a main cavity forming a substantial portion of the inner aspects of the blade inside the inner wall of the housing of the blade. The main cavity may have any shape sufficient to provide cooling gas to various portions of the blade; however, this invention is not limited by the shape of the main cavity. The cavity defined by the inner wall and the outer wall may include one or more protrusions or one or more pedestals, or both, for increasing the rate of convection of the cooling system. In at least one embodiment, the cavity may include a plurality of pedestals extending from the inner wall to the outer wall. The pedestals may be positioned in the cavity in a plurality of rows or in other manners. The rows may be generally parallel with a longitudinal axis of the blade, may be generally orthogonal to a direction of an average flow of gas through the cavity, or may be positioned in other manners. In one or more embodiments, the pedestals in a second row may be offset relative to pedestals in a first row immediately upstream from the second row.
The cavity positioned between the inner and outer walls forming the housing may also include one or more protrusions. The protrusions, which may also be referred to as fences, may introduce turbulence to a gas flowing through the cavity. The protrusions may be positioned generally parallel with the longitudinal axis of the blade, may be generally orthogonal to a direction of an average flow of gas through the cavity, or may be positioned in other manners. In at least one embodiment, the protrusions may be positioned between pedestals. The protrusions may be positioned between each pedestal in a row of pedestals or only between a portion of the pedestals forming a row.
In at least one embodiment, the cavity may include a first row of pedestals having protrusions positioned between at least two pedestals. The protrusions may be coupled to an inner wall of the housing. The cavity may further include a second row of pedestals positioned immediately downstream from the first row and generally parallel to the first row. The first and second row may be positioned generally parallel to the longitudinal axis of the blade, may be generally orthogonal to a direction of an average flow of gas through the cavity, or may be positioned in other manners. The second row of pedestals may include one or more protrusions positioned between the pedestals and attached to the outer wall of the housing. Alternatively, the first row may have protrusions attached to the outer wall and the second row may have protrusions attached to the inner wall. This pattern may continue for a portion or all of the cavity located between the outer and inner walls forming the housing.
The pedestals in the second row may be offset from the pedestals in the first row. By offsetting the pedestals in the second row relative to the pedestals in the first row positioned upstream from the second row and by alternating the protrusions from the inner wall to the outer wall, or vice versa, a spiral flow of gas may be created in the cavity. The spiral flow increases the rate of convection and thus increases the cooling capacity of the cooling system. In addition, by including a protrusion in the first row of pedestals, turbulence is induced immediately to the flow of gas entering the cavity. Because turbulence increases the rate of convection, the turbulent action created by the protrusions in the first row increases the rate of convection of the cooling system. These and other embodiments are described in more detail below.